Related fields include semiconductor devices and their fabrication; in particular, thin-film components included in individual cells of non-volatile memory based on resistive switching (ReRAM).
Nonvolatile memory elements are used in computers and other devices requiring persistent data storage (e.g., cameras, music players). Some traditional nonvolatile memory technologies (e.g., EEPROM, NAND flash) have proven difficult to scale down to smaller or higher-density configurations. Therefore, a need has developed for alternative nonvolatile memory technologies that can be scaled down successfully in terms of performance, reliability, and cost.
In resistive-switching-based nonvolatile memory, each individual cell includes a resistor that is bistable; it can be put into either of two states (a low-resistance state LRS or a high-resistance state HRS), and will stay in that state until receiving the input that changes it to the other state. The state of the bistable memory cell represents a bit value (e.g., the LRS may represent “1” and the HRS may represent “0”). The cell is thus “written” to by changing its resistance value. The cell is “read” by measuring its resistance in a way that does not change it. Ideally, write and read operations should require as little power as possible, both to conserve energy and to avoid generating unwanted heat.
Repeatability of the resistance values of “0” and “1” from cycle to cycle, as well as consistency of these values from cell to cell, can affect the power required to operate the cell. The larger the “error bars” around the LRS and HRS, the more different they need to be in order to be reliably read even in the worst case of expected error, which can often mean more power used for writing the cell.